1. Field of the Invention
The present invention relates to a battery information acquiring apparatus that acquires battery information of a battery cell in a battery pack including a plurality of the battery cells connected in series and transmits the battery information to a management unit that manages the battery pack.
2. Related Art
As supply of battery power for electric cars or industrial vehicles, battery packs in which many battery cells of low voltage and low capacity are connected in series or in parallel are used to obtain a high voltage and high capacity voltage. Safe operation of a battery pack requires a battery information management system that monitors battery information such as a voltage and temperature of each battery cell.
A conventional battery information management system has a plurality of battery information acquiring modules each including a battery cell, battery information acquiring circuit and transmitting/receiving circuit (communication circuit) and carries out communication and control between the management unit and each battery information acquiring module (see JP-A 11-345622 (Kokai)).
Each battery information acquiring module receives a supply of power and GND from the respective battery cells all the time, and therefore there is a problem that power is consumed even during standby during which control signals and battery information are not communicated with the management unit.
Furthermore, the respective battery information acquiring modules transmit battery information acquired from their respective battery cells to the management unit using differential signals, and in this case, differential signals transmitted from the respective battery information acquiring modules have different common mode voltages. For this reason, it is necessary to connect two wires from each battery information acquiring module to the management unit respectively and carry out transmission through the respective wires. This results in a problem of making wiring more complicated.
Furthermore, the management unit side also has a problem that it is necessary to have a function of shifting the levels of signals of common mode voltages that vary from one battery information acquiring module to another and secure their withstand voltages.